Cathode positioning retainer

ABSTRACT

This relates to improved cathode retainer means for effecting positive positioning of a cathode within a companion electrode structure for use in a cathode ray tube electron gun. An endemitting cathode is affixed within the aperture of a ceramic insulator disc and thence suitably positioned within a control grid electrode by an improved retainer means fabricated to exert sustained pressure against the supporting insulator. The improved retainer has a plurality of terminally oriented instanding projections of a bilaminate metallic material of predetermined flexure performance which are oriented to abut the insulator. Such bilaminate material comprises a first lamina of an active metallic alloy contiguously bonded along a common interface to a second lamina of a passive alloy material. The active alloy portion upon being subjected to a predetermined temperature during tube processing undergoes a metallurgic phase transformation effecting a volume change therein producing a definite modification of the shaping of the retainer projections thereby exerting positive and sustained pressure against the cathode positioning insulator.

Bowes et a1.

[ CATHODE POSITIONING RETAINER v [75] Inventors: Robert J. Bowes; JohnJ. Miller,

both of Seneca Falls, NY.

[73] Assignee: GTE Sylvania Incorporated, Seneca Falls, NY.

[22] Filed: June 29, 1973 [21] Appl. No.: 375,181

[52] US. Cl 313/268, 313/DIG. 1, 313/292 [51] Int. Cl l-I0lj 29/48, HOlj1/94 [58] Field of Search 313/D1G. l, 268, 270, 281, 313/292 [56]References Cited UNITED STATES PATENTS 2,476,060 7/1949 Moss 313/2682.527.127 10/1950 Gormley ct al...'... 313/292 3,311,774 3/1967 Atti313/270 3,743,485 7/1973 Gottlicb ct al 148/34 FOREIGN PATENTS ORAPPLICATIONS 763,951 12/1956 Grcat Britain 3l3/DlG. 1

Primary E.\'aminerJames W. Lawrence Assistant Examiner-Wm. H. PunterAttorney, Agent, or Firm N0rman J. OMalley; Frederick H. Rinn; Cyril A.Krenzer 1 July 30, 1974 [57] ABSTRACT This relates to improved cathoderetainer means for effecting positive positioning of a cathode within acompanion electrode structure for use in a cathode ray tube electrongun, An end-emitting cathode is affixed within the aperture of a ceramicinsulator disc and thence suitably positioned within a control gridelectrode by an improved retainer means fabricated to exert sustainedpressure against the supporting insulator; The improved retainer has aplurality of terminally oriented instanding projections of a bilaminatemetallic material of predetermined flexure performance which areoriented to abut the insulator. Such bilaminate material comprises afirst lamina of an active metallic alloy contiguously bonded along acommon interface to a second lamina of a passive alloy material. Theactive alloy portion upon being subjected to a predetermined temperatureduring tube processing undergoes a metallurgic phase transformationeffecting a volume change therein producing a definite modification ofthe shaping of the retainer projections thereby exerting positive andsustained pressure against the cathode positioning insulator.

8 Claims, 9 Drawing Figures 1 CATHODE POSITIONING RETAINER BACKGROUND OFTHE INVENTION This invention relates to means for positioning a cathodestructure'within an electron discharge device and more particularly tomeans for effecting positive positioning of a cathode within a companionelectrode structure for use in a cathode ray tube.

In the manufacture of cathode ray tubes it has been conventionalpractice to employ cathodes utilizing heat responsive electron emissivematerials as a source of electron beam energy. In devices of thisnature, the

cathode usually comprises a tubular metal sleeve capped on one end witha closure portion having electron emissive material adhered to theexterior surface thereof. A heater or resistive element is suitablydisposed within the cathode tube to furnish the temperature levelrequired to produce thermionic emission from the emissive material. Aceramic insulating disc having an axial opening therein to accommodatethe cathode is utilized in a number of CRT electron guns to orient andsupport the cathode within a substantially cup-shaped control gridelectrode having a defined aperture in the closed end thereof.

It is operationally essential to have the cathode positioned in a mannerthat the emissive material terminally disposed thereon is properlyoriented and spaced relative to the associated control electrodeaperture. It is also important that the cathode be securely disposed inits supporting wafer relative to the adjacent grid electrode to assurean adequate electrical insulative area or barrier therebetween.Furthermore, for proper operation of the tube, the cathode supportinginsulator must be securely positioned within the associated encompassingelectrode in a manner to prevent microphonics emanating from loosenessof elements in the assembly.

The tubular cathode is disposed within the opening of the insulator discand affixed therein by means of swages or ferrules which contact thesupporting ceramic disc completely around the cathode member. Anassociated spacer means is positioned between the insulator disc and theelectrode closure portion to effect predetermined spacing between theend-emitting surface of the cathode and the related aperture of theelectrode. With the insulator disc being so positioned against thespacer means, a retainer for maintaining positioning of the disc withinthe grid electrode is inserted within the electrode in a manner to abutthe under surface of the insulator and effect contiguous placementthereof against the spacer means. Being so positioned, the retainer isthen bonded to the sidewall of the electrode thereby producing anintegrated structure. In certain instances, it has been found that, dueto operational thermal expansion and contraction, the components of thecathode electrode structure develop a degree of looseness which is avery undesirable condition. The factor of tightness assumes greatimportance in color cathode ray tube applications wherein it isimperative to have the cathode rigidly supported within the electrodestructure. Any looseness of the cathode varies the critical operationalcathode-to-grid spacing thereby generating spurious signals ormicrophonics which are visibly manifest during tube operation.

OBJECTS AND SUMMARY OF THE INVENTION It is an object of the invention toreduce the aforementioned disadvantages and to provide an improved meansfor effecting positive positioning of a cathode within the associatedelectrode structure. Another object is to utilize tube processingtemperature to effect positive tightness between the components of theintegrated cathode electrode structure.

These and other objects and advantages are achieved in one aspect of theinvention by providing an integrated cathode grid assembly wherein theceramic spacer means supporting the cathode is positionally and rigidlyheld by an improved insulator retainer. This modified retainer is formedto have a plurality of terminally oriented instanding projections of abilaminate metallic material of predetermined flexure performance whichare oriented to abut the under surface of the cathode supportinginsulator. The bilaminate material comprises a first laminaof activealloy material contiguously bonded along a common interface to a secondlamina of a passive'alloy material. The active lamina portion of thematerial undergoes a metallurgical phase transformation at apredetermined temperature during tube processing to effect a flexuralstress in the projections contiguous to the cathode supporting insulatorthereby modifying the bilaminate means to a substantially permanentsecondary structural shape, the stress of which exerts positive andsustained pressure against the insulator.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional viewillustrating a cathode-grid electrode assembly for use in a cathode raytube electron gun. As shown, the cathode affixed within the supportinginsulator is positioned within the control grid electrode and locatedtherein by suitable spacer and retainer means; and

FIGS. 2a through 5b are respective plan and cross sectional viewsshowing various embodiments of the cathode insulator retainer structureof the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS For a better understanding ofthe present invention, together with other and further objects,advantages and capabilities thereof, reference is made to the followingspecification and appended claims in connection with the aforedescribeddrawings.

With reference to FIG. 1, there is shown a representation of thecathode-control grid assembly portion 11 of a cathode ray tube electrongun. The control grid 13, for'example, is a substantially cup-shapedelectrode having an end closure 15 with a defined aperture 17therethrough and an encompassing sidewall 19 therearound of a giveninternal dimensioning. Positioned within this control grid electrode isa cathode supporting insulator 21 having transverse dimensioning smallerthan the internal dimensioning of the electrode member and formed tohave an opening 23 therethrough wherein the tubular cathode 25 isaffixed by ferruletype modifications. A compatibly formed spacer means27 is positioned between the cathode supporting insulator 21 and thegrid electrode closure portion 15 to effect predetermined spacingbetween electron emitting surface 29 of the cathode and the aperture 17in the grid electrode. An insulated thermionic heater means 31 issuitably disposed within the tubular cathode, being positioned throughthe open end thereof.

An insulator retainer 33 externally dimensioned to slide within the gridelectrode, is abutted against the cathode supporting insulator 21 andaffixed to the sidewall 19 of the control grid electrode 13 to effectcontiguous placement of the insulator 21 against the spacer means 27.The retainer 33 has a plurality of terminally oriented instandingprojections 35 of a bilaminate metallic material 37 of predeterminedflexure performance. This material is comprised of a first lamina 39 ofan active alloy material contiguously metallurgically bonded along acommon interface 41 to a second lamina 43 of a passive alloy material.The active alloy material has the capability, on being subjected to apredetermined temperature, to undergo a metallurgical phasetransformation effecting a shrinking volume change and resultantdeformation thereof, while the passive alloy material has the capabilityof remaining in a substantially stable metallurgical phase throughoutthe temperature range wherein the predetermined temperature is included.This bilaminate material and the representative alloys comprising thesame are the subject of a separate patent application, Ser. No. 206,124,now U.S. Pat. No. 3,743,485 filed Dec. 8, I97], and acontinuation-in-part patent application, Ser. No. 373,400, filed June25, l973,by Arnold J. Gottlieb and George A. Majesko and assigned toWilbur B. Driver Company, Newark, N.J.,'which is a subsidiary of theassignee of the present invention. These patent applications disclosebilaminate materials for utilization in existing structures wherein thecharacteristics of thematerials provide improved results thereof. In thepresent application, the generic bilaminate material of Ser. No. 206,124is put to new usage in a newly designed retainer structure to provideresults heretofore unattained.

FIGS. 2a and 2b delineate in greater detail the improved retainer meansillustrated in FIG. 1. In this embodiment the whole of the retainer 33is fabricated from the aforementioned bilaminate material. A pluralityof spaced apartterminally oriented instanding projection's 35 areintegral extensions of material comprising the encompassing sidewall 36.The retainer structure is formed in a manner that the active materiallaminate'portion 39 of the bilaminatematerial is oriented proximal tothe cathode supporting insulator member 21. Prior to being incorporatedinto the cathodecontrolgrid assembly, the improved retainer structure isformed to have a primary shape wherein the tab like radially instandingprojections 35 are oriented substantially normal to the sidewall portion36. During electron gun assembly, these tab like projections are placedcontiguous to the cathode supporting insulator, and upon reaching apredetermined transformation temperature during tube processing ametallurgical phase change takes place in the active lamina of thestructure thereby modifying the bilaminate means to a secondarystructural shape which tends to exert positive and sustained pressureagainst the under surface of the insulator 21.

The predetermined temperature at which the active alloy lamina of thebilaminate material undergoes the desired metallurgic phasetransformation is above the temperature level encountered in toto by thebilaminate material during retainer fabrication and subsequent tubeassembly. The active alloy portion of the bilaminate material is onethat has a phase transformation temperature that is within the thermalrange encountered during subsequent tube processing.

In an operating CRT electron gun, the insulator retainer componentreaches a maximum temperature in the neighborhood of 340 C, but duringprocessing of the tube the retainer is subjected to a varied range oftemperatures. For example, during sealing of the electron gun mount intothe envelope, a temperature of about 300 C is reached; during exhaustbreakdown a thermal level in the vicinity of 650 C is encountered,

and when associated heater conditioning is 'accomplished, thetemperature is elevated to around 720 C. During subsequent cathode agingthe retainer reaches a temperature of approximately 580 C. Inconsidering the foregoing range of thermal levels, it is preferred thatthe metallurgical phase transformation of the active lamina material 39takes place at. a temperature level encountered early in the tubeprocessing procedure so that the advantageous effects of thetransformation can be beneficially utilized in a rigidly tightenedcathode-electrode assembly during the remaining stages of processing.

An alloy suited for the active lamina portion of the bilaminate materialis an iron-nickel alloy consisting essentially of 32 to 33 percent byweight of nickel with the balance of iron. The phase changetransformation temperature of this alloy is about 300 C. One passivematerial for use with the above-noted active lamina is anotheriron-nickel alloy consisting essentially of about 36 percent by weightof nickel, and the balance'of iron. Another suitable passive materialfor use in this combination is 1010 steel.

At the phase transformation temperature, the active material lamina ofthe projections 35 undergoes a crystal structure transformation from'themartensitic phase to the austenitic phase whereat the active materialshrinks in volume thereby deforming and inducing flexural stress in thebilaminate projections causing them to bend arcuately upward, asphantomed at 45,.to exert increased pressure against the insulator disc21. As previously mentioned, the active and passive alloy materials ofthe bilaminate structure are selected to have the phase transformationtemperature of the active material within the tube processingtemperature range, that is above about 300C and below about 700 C. Inother words, the passive material should remain in a stablemetallurgical phase throughout the temperature range encountered by thematerial which should be up to substantially 800 C. When the criticaltemperature of phase transformation is reached, a modification of theshape of the structure is triggered by the active material and suchchange of shape is substantially permanently retained by the structure,the coefficients of thermal expansion of the active and passive laminaebeing substantially equal. Thus, the added flexural stress of thetransformed material of the retainer will be sustained against thecathode supporting insulator regardless of the temperatures normallyencountered thereafter in further tube processing and subsequentoperation.

Another or second embodiment 47 of the improved I cathode supportingretainer is shown in FIGS. 3a and 3b. In this embodiment the bodyportion 49 of the retainer member is made of a material such asstainless steel having a slightly inturned terminal edge 51 where upon aplurality of separate spaced apart strips 53 of bilaminate material aresuitably bonded as, for example, by small area spot welds'55. The heatassociated with the spot welding effects only minute and inconsequentialareas of transformation. These radially oriented bilaminate strips 53have the active alloy portion 39 facing outward in a mannerto makecontact with the under surface of the insulator 21. Upon the temperatureconsummated phase transformation, these strips each deform in an arcuatemanner, as phantomed at 57, to exert increased pressure against theinsulator disc.

Still another or third embodiment 59 of the invention is shown in FIGS.4a and 4b wherein the retainer body 61 is fabricated of a material suchas stainless steel. Attached to the terminal end 63 thereof are aplurality of substanially L-shaped bilaminate members 65 spaced apartand affixed to the internal surface of the retainer member 61 by smallarea spot welds 67. These L- shaped 'configurated members, having theactive lamina 39 on the outer side of the L, are located in a manner toextend beyond the terminal edge 63 of the retainer member. Suchorientation allows for flexural stress or induced movement in twodirections, substantially upward and outward as indicated by arrows 69and 71 respectively.

An additional or fourth embodiment 73 of the invention is illustrated inFIGS. 5a and 5b, wherein the retainer member 75 is formedof bilaminatematerial having aplurality of separate arcuate ledges 77 oriented insubstantially common plane, with the active lamina 39 being upwardlyoriented. Each of these ledges is integral with theterminal periphery 79of .the retainer and extendin an inward mannertherefrom. Each of thearcuate ledges has a pair of terminal apices 81 and 81'. When thisembodiment of the retainer is subjected to the phase transformationtemperature during tube processing, the inward portion of each arcuateledge, in the vicinity of the apices, is subjected to greaterdeformation whereby the apices make substantially pressured two-pointcontact with the insulator disc 21.

Thus, several embodiments of an improved cathode positioning retainingstructure has been described whereby a cathode retainer providespositive and sustained pressure to the cathode supporting insulatorin amanner to permanently tighten the cathode-grid assembly. Such sustainedpressure is expeditiously achieved by phase structure transformation ofa portion of the bilaminate material of the retainer.

While there has been shown and described what are at present consideredthe preferred embodiments of the invention, it will be obvious to thoseskilled in the art that various changes and modifications may be madetherein without departing from the invention as defined by the appendedclaims.

What is claimed is:

1. In a cathode ray tube electron gun structure, improved means foreffecting positive positioning of a cathode within a substantiallycup-shaped associated electrode having an end closure with an aperturetherethrough and an encompassing sidewall therearound of given internaldimensioning, said improved positioning means comprising:

a supporting insulator disc having transverse dimensioning smaller thanthe internal dimensioning of said electrode and formed to have anaperture therethrough, said cathode being oriented within the apertureof said supporting insulator;

spacer means positioned between said insulator and said electrodeclosure portion to effect predetermined spacing between the emittingsurface of said cathode and the aperture of said electrode; and

an insulator retainer externally dimensioned to slide within saidelectrode and be affixed to the sidewall thereof in a manner to abutsaid insulator and ef fect contiguous placement thereof against saidspacer means, said retainer having a plurality of terminally orientedinstanding projections of a bilaminate metallic material ofpredetermined flexure performance, said material being formed of a firstlamina of active alloy material contiguously metallurgically bondedalong a common interface to a second lamina of a'passive alloy material,said active alloy material upon being subjected to a predeterminedtemperature undergoes a metallurgical phase transformation effecting avolume change thereof, said passive material remaining in asubstantially stable single metallurgical phase state throughout atemperature range wherein said predetermined temperature is included,said predetermined temperature being above the temperature encounteredin toto by said bilaminate means during retainer fabrication andsubsequent tube assembly, said predetermined temperature being a thermallevel encountered during subsequent tube processing, said bilaminatemeans having a formed primary shape prior to being incorporated intosaid electrode, the active lamina portion of said primary shaped meansof said retainer upon reaching said predetermined temperature duringtube processing transforms to said metallurgical phase thereby modifyingsaid bilaminate means to ase'condary structural shape to exert positiveand sustained pressure against said insulator.

2. The improved cathode positioning means according to claim 1 whereinsaid insulator retainer is comprised of said bilaminate material andwherein said terminally oriented instanding projections are integralextensions of said material.

3. The improved cathode positioning means according to claim 1 whereinthe terminally'oriented instanding bilaminate projections of saidinsulator retainer are separate spaced apart strips bonded to theterminal portion of said retainer and extended radially inwardtherefrom.

4. The improved cathode positioning means according to claim 1 whereinsaid instanding projections associated with said retainer means are inthe form of a plurality of separate arcuate ledges oriented in asubstantially common plane, each of said ledges being integral with theterminal periphery of said retainer.

5. The improved cathode positioning means according to claim 1 whereinthe active material laminate portion of said bilaminate material isoriented proximal to the insulator member.

6. The improved cathode positioning means according to claim 1 whereinthe predetermined phase transformation temperature of said activematerial lamina portion of said projections is above about 250 C andbelow about 700 C.

7. The improved cathode positioning means according to claim 1 whereinthe active material lamina of said bilaminate means undergoes a crystalstructure transformation from the martensitic phase to the austeniticphase at said predetermined temperature and when transforming from amartensitic to the austenitic phases thereby inducing flexural stress insaid projections to exert positive and sustained pressure against saidinsulator.

1. In a cathode ray tube electron gun structure, improved means foreffecting positive positioning of a cathode within a substantiallycup-shaped associated electrode having an end closure with an aperturetherethrough and an encompassing sidewall therearound of given internaldimensioning, said improved positioning means comprising: a supportinginsulator disc having transverse dimensioning smaller than the internaldimensioning of said electrode and formed to have an aperturetherethrough, said cathode being oriented within the aperture of saidsupporting insulator; spacer means positioned between said insulator andsaid electrode closure portion to effect predetermined spacing betweenthe emitting surface of said cathode and the aperture of said electrode;and an insulator retainer externally dimensioned to slide within saidelectrode and be affixed to the sidewall thereof in a manner to abutsaid insulator and effect contiguous placement thereof against saidspacer means, said retainer having a plurality of terminally orientedinstanding projections of a bilaminate metallic material ofpredetermined flexure performance, said material being formed of a firstlamina of active alloy material contiguously metallurgically bondedalong a common interface to a second lamina of a passive alloy material,said active alloy material upon being subjected to a predeterminedtemperature undergoes a metallurgical phase transformation effecting avolume change thereof, said passive material remaining in asubstantially stable single metallurgical phase state throughout atemperature range wherein said predetermined temperature is included,said predetermined temperature being above the temperature encounteredin toto by said bilaminate means during retainer fabrication andsubsequent tube assembly, said predetermined temperature being a thermallevel encountered during subsequent tube processing, said bilaminatemeans having a formed primary shape prior to being incorporated intosaid electrode, the active lamina portion of said primary shaped meansof said retainer upon reaching said predetermined temperature duringtube processing transforms to said metallurgical phase thereby modifyingsaid bilaminate means to a secondary structural shape to exert positiveand sustained pressure against said insulator.
 2. The improved cathodepositioning means according to claim 1 wherein said insulator retaineris comprised of said bilaminate material and wherein said terminallyoriented instanding projections are integral extensions of saidmaterial.
 3. The improved cathode positioning means according to claim 1wherein the terminally oriented instanding bilaminate projections ofsaid insulator retainer are separate spaced apart strips bonded to theterminal portion of said retainer and extended radially inwardtherefrom.
 4. The improved cathode positioning means according to claim1 wherein said instanding projections associated with said retainermeans are in the form of a plurality of separate arcuate ledges orientedin a substantially common plane, each of said ledges being integral withthe terminal periphery of said retainer.
 5. The improved cathodepositioning means according to claim 1 wherein the active materiallaminate portion of said bilaminate material is oriented proximal to theinsulator member.
 6. The improved cathode positioning means according toclaim 1 wherein the predetermined phase transformation temperature ofsaid active material lamina portion of said projections is above about250* C and below about 700* C.
 7. The improved cathode positioning meansaccording to claim 1 wherein the active material lamina of saidbilaminate means undergoes a crystal structure transformation from themartensitic phase to the austenitic phase at said predeterminedtemperature and wherein the coefficients of thermal expansion of saidactive and passive laminae are substantially equal.
 8. The improvedcathode positioning means according to claim 1 wherein the activematerial lamina portion of said bilaminate materials shrinks in volumewhen transforming from a martensitic to the austenitic phases therebyinducing flexural stress in said projections to exert positive andsustained pressure against said insulator.